1. Field of the Invention
The present invention relates to a dampening device for ball game rackets, in particular tennis, squash, racquetball, badminton or paddle tennis rackets, which can be fixed in particular to a stringing and/or a frame of the ball game racket. Moreover, the present invention relates to a ball game racket comprising a dampening device of this kind. A method for manufacturing a racket of this kind and a method for fixing a device of this kind to a ball game racket are described as well.
Ball game rackets of the above-mentioned type comprise a frame having a head region for retaining a stringing and a handle or grip portion. Rackets of this kind can also comprise a heart or throat region or fork being arranged between the head region and the grip portion.
When striking a ball with the racket, the racket, in particular the stringing and the frame, is first deflected by the ball. After the ball has deflected the racket, the ball flies away from the bent or deflected racket. After separation from the ball, the racket begins to vibrate in its free dampened vibration (natural or characteristic frequency). In particular the vibrations generated when the ball hits the strings of the racket are transmitted to the arm of the user. Such forces or shocks or vibrations caused by striking a ball are, at least when acting for a long time, i.a. responsible for health problems of the player, such as for instance the so-called tennis elbow. Furthermore, a continuous compensation of the impact shock and the forces occurring during the game make the player quickly tired. Moreover, the control of the racket and thus the playability behavior are influenced by too strong forces and vibrations acting on the player. Moreover, the vibrations of the string that was excited by the strike are often sensed as being disturbing. This is because the frequency of the vibrations of the excited strings lies at least partially in the audible range.
2. Description of Related Art
Dampening devices for ball game rackets are generally known. DE-U-84 051 02 describes a means for dampening the vibration in the stringing of ball striking devices, which consists of crossing longitudinal and transverse strings and comprises a coupling member that acts as a vibration dampening element and couples at least two longitudinal strings in at least one of their end regions mechanically. To this end, the coupling member is configured as an elastic element comprising a retainer for the longitudinal strings by means of which the longitudinal strings are spaced from each other at a distance which preferably differs from the distance between the longitudinal strings to be coupled. The retainer for the longitudinal strings to be coupled comprises retainer sleeves that can be pushed over these strings, and the coupling member comprises at least one further retainer in the form of a hole for a transverse string.
U.S. Pat. No. 4,732,383 describes a shock and vibration absorber for rackets, which is configured as a bar and weaved over and under the longitudinal strings in a region between the grip and the nearest transverse string. This absorber extends across the entire width of the racket in this region, wherein the ends are fixed in the spaces between the frame and the nearest longitudinal strings. The bar-shaped absorber is composed of a plurality of layers of a shock-and-frequency absorbing material which is soft, light and resilient.
EP-A-0 497 561 relates to a vibration damper for ball game rackets, which is configured as a flexible, rubber-like strap having dampening characteristics, wherein the flexible strap comprises a body portion with opposing sides and with a plurality of transversely extending ribs formed thereon in spaced apart longitudinal relation as well as end portions which are integrally connected with the body portion of the flexible strap, wherein the flexible strap is fixed by means of fixing means to adjacent longitudinally extending sides of the racket head and interwoven with the strings.
DE-A-35 041 37 discloses a ball game racket in which at least one dampening means can be fixed to the stringing in a frame for dampening the vibrations after striking the ball, wherein the respective dampening means is inserted into free fields formed by strings of a stringing and is held in a form-fit manner by the strings of the stringing.
U.S. Pat. No. 4,776,590 discloses a dampening means for ball game rackets, which is formed by a block of viscoelastic foam and inserted between the strings of the racket stringing, wherein the compressed block typically engages four neighboring strings.
AT-B-352 590 describes a means for absorbing vibrations in ball game rackets, wherein at least two longitudinal strings of the stringing are mechanically coupled preferably at the heart-side end thereof by means of a vibration absorber, the vibration absorber being arranged outside the region of the transverse strings.
GB-2 191 409 relates to a ball game racket comprising a dampening means having a plurality of holes through which the longitudinal strings of the racket stringing are led, wherein the dampening means is arranged in the stringing region below the transverse strings so as to adjoin the racket frame and fixed by means of a fixing means led from outside through the holes of the racket frame that serve for retaining the stringing.
Further, different kinds of dampening means are disclosed, e.g., in JP-A-03231689, EP-A-0 642 811, EP-A-0 261 994, U.S. Pat. No. 4,190,249, DE-A-37 24 205, DE-A-39 10 890, WO-A-8802271, DE 10 2004 025 346 A1, EP-A-0 441 971 and WO-A-9009215.
These known dampening devices are not satisfying in view of their dampening characteristics, in particular with respect to the vibrations transmitted to the player and the acoustic effects of the vibrations, their fixing requirements, their relatively involved and thus expensive production and/or their high weight. Furthermore, they do not or only insufficiently influence the vibrations of the frame or the transmission of the string vibrations to the frame.